The vertebrate immune system is characterized by its ability to respond to an enormously diverse set of antigenic determinants. This capability is due to the synthesis by the body of a set of glycoproteins whose specificity for a single antigen is determined by a variable sequence of amino acids which binds to the antigen. The glycoproteins, which recognize and bind free antigens, are produced by B cells and are called immunoglobulins (Ig).
Each B cell, or bone marrow-derived lymphocyte, produces antibody specific for only one antigen. It has been theorized that the type of immunoglobulin which is produced by the B cell is generated by a series of gene rearrangements and RNA splicing events that result in polypeptide chains consisting of variable and constant regions. These regions can be subdivided into domains held together by interchain and intrachain disulfide bridges situated at the same relative positions. The characteristic primary and secondary structure is made up of heavy and light chains which begin with a leader peptide of 17-29 residues, followed by a variable (V) region of 94-97 residues, then a joining region of 13-17 residues (J), then a constant region (C). The domains of the constant regions of the immunoglobulins are encoded by separate exons from those for the variable region and do not appear to rearrange during development.
T cells or Thymus derived lymphocytes, like B cells, are capable of recognizing a wide range of different antigens. The ability to recognize a given antigen is also fixed in any particular clonal line of T cell. T cells, however, recognize only antigens located on the surfaces of cells in the specific molecular context of self major histocompatability complex (MHC) gene products, not freely circulating antigens. Two types of T cell receptors have been proposed: those which recognize foreign antigens (such as viral antigens) in the molecular context of the T cell host's self-MHC gene products and those which recognize foreign MHC gene products. Cell surface antigens include tumor cell and viral antigens. The ability to recognize cell-bound antigens is acquired when the T cells differentiate in the host thymus.
Effective antisera and monoclonal antibodies have now been developed which recognize and precipitate clone-specific proteins on the surface of functional T cell clones, hybridomas or T cell tumors. Studies using these antibodies have suggested that the specificity--determining portion of a T cell receptor is a heterodimeric glycoprotein of about 90,000 daltons and consisting of a 40-45,000 dalton alpha subunit and a 42-44,000 dalton beta subunit. Peptide fingerprint analysis suggested that both subunits were composed of variable and constant regions.
Two groups of workers have since succeeded in isolating T cell-specific cDNA (complementary DNA) clones of mouse or human origin which are homologous to immunoglobulin genes. S. M. Hedrick, E. A. Nielsen, J. Kevaler, D. I. Cohen, and M. M. Davis, as reported in Nature, 308:153-158 (1984), have shown that the cDNA encodes a protein composed of an amino terminal variable and a carboxy-terminal constant region. They also showed that the corresponding genomic DNA sequences had undergone clone-specific somatic rearrangements in various T cell lines.
Y. Yanagi, Y. Yoshikai, K. Leggett, S. P. Clark, I. Aleksander, and T. W. Mak, in Nature, 308:145-149 (1984) reported the nucleotide sequence of a cDNA clone derived from the human leukaemic T cell line, MOLT-3. The predicted amino acid sequence encoded by the human cDNA clone of Yanagi et al. is highly homologous in the constant region to the cDNA clone isolated by Hedrick et al. from an antigen specific, MHC-restricted T helper cell hybridoma. Due to the substantial homology between the sequences of Hedrick et al and Yanagi et al it is likely that they represent one subunit of the T cell receptor.
It is therefore an object of the present invention to provide a T cell receptor gene or nucleotide sequence which codes for subunits of the T cell receptor.
It is a further object of the present invention to provide murine cDNA clones which code for a subunit of the T cell receptor.
It is a still further object of the present invention to provide hybridization probes for identifying and isolating the T cell receptor genes and subunits of the T cell receptor genes of other, non-mouse species, including the human specie.
Another object of the present invention is to provide the protein or amino acid sequence of a murine alloreactive cytotoxic T lymptocyte receptor.
It is yet another object of the present invention to provide specific antibodies to the T cell receptor and subunits of the T cell receptor which are useful for identification, isolation, and in other methods for which antibodies are useful such as in delivering antibody bound drugs to a specific cell.